Metal fibers have been applied to construct composites with desirable electromagnetic interference shiel ding effectiveness and mechanical properties. Copper and stainless steel fibers were prepared with micro-saw fib...Metal fibers have been applied to construct composites with desirable electromagnetic interference shiel ding effectiveness and mechanical properties. Copper and stainless steel fibers were prepared with micro-saw fiberpulling combined cutting method. The cross section of the fibers is hook-like, which is beneficial to the improvement of bonding strength. Cement-based composites with copper and stainless steel fibers were fabricated and their electromagnetic shielding effectiveness was measured in the frequency range of 1 - 5 GHz. The results show that the electromagnetic interference shielding effectiveness of those composites is enhanced by the addition of metal fibers,which functions mainly due to the absorption. At some frequencies, 20 dB or more difference is obtained between the materials with and without metal fibers.展开更多
A novel classification algorithm based on abnormal magnetic signals is proposed for ground moving targets which are made of ferromagnetic material. According to the effect of diverse targets on earth's magnetism,t...A novel classification algorithm based on abnormal magnetic signals is proposed for ground moving targets which are made of ferromagnetic material. According to the effect of diverse targets on earth's magnetism,the moving targets are detected by a magnetic sensor and classified with a simple computation method. The detection sensor is used for collecting a disturbance signal of earth magnetic field from an undetermined target. An optimum category match pattern of target signature is tested by training some statistical samples and designing a classification machine. Three ordinary targets are researched in the paper. The experimental results show that the algorithm has a low computation cost and a better sorting accuracy. This classification method can be applied to ground reconnaissance and target intrusion detection.展开更多
When a gun fires the diffusion of chemical species from the propellant gas, such as CO, CO2, H2, H2O and N2, into the hot surface through the microcracks forms reaction products and speeds up the erosion process.There...When a gun fires the diffusion of chemical species from the propellant gas, such as CO, CO2, H2, H2O and N2, into the hot surface through the microcracks forms reaction products and speeds up the erosion process.Therefore, crack repairing and healing can be a possible measure for protecting against erosion of gun bore. The present study develops a novel nanocomposite with the size of 30 - 150 nm to repair and heal the microcracks so that the propellant gas can be prevented from reacting with the steel. Sample of gun steel 40CrNiMoV plate (10 mm× 10 mm × 2 mm) is prepared and a fishtail crack is generated through a repeated plastic deformation process. The crackrepairing results show that the fishtail crack become shorter and narrower. A new phase is formed, which is found to have the elements, such as Ca, La, from the raw materials of nanocomposite by energy spectrum analysis.展开更多
The composite films consisting of the titania gel impregnated with hydroxyapatite （HAP） submicron particles were prepared on commercial Ti6A14V plates processed by a sol-gel route. HAP powders were synthesized based...The composite films consisting of the titania gel impregnated with hydroxyapatite （HAP） submicron particles were prepared on commercial Ti6A14V plates processed by a sol-gel route. HAP powders were synthesized based on wet chemical precipitation method with Ca（NO3）2.4H2O and （NH4）2HPO4 as starting reagents. After being calcined at 900℃, HAP powders were ultrasonically scattered in ethanol to produce HAP sol. The titania sol was prepared using titanium （IV） isopropoxide {Ti[OCH（CH3）2]4} as precursor. Both the titania sol and the HAP/titania mixture were sequentially spin-coated on the substrates and calcined at various temperatures. The characteristics and mechanical adhesion of the composite films were investigated. The results show that the as-prepared films are dense, homogeneous, well-crystallized, and there is a good interfacial adhesion between the film and the substrate. The in vitro bioactivities of these films were discussed based on the analysis of the variations of Ca and P concentrations in the simulated body fluid and their surface morphologies against immersion time.展开更多
文摘Metal fibers have been applied to construct composites with desirable electromagnetic interference shiel ding effectiveness and mechanical properties. Copper and stainless steel fibers were prepared with micro-saw fiberpulling combined cutting method. The cross section of the fibers is hook-like, which is beneficial to the improvement of bonding strength. Cement-based composites with copper and stainless steel fibers were fabricated and their electromagnetic shielding effectiveness was measured in the frequency range of 1 - 5 GHz. The results show that the electromagnetic interference shielding effectiveness of those composites is enhanced by the addition of metal fibers,which functions mainly due to the absorption. At some frequencies, 20 dB or more difference is obtained between the materials with and without metal fibers.
基金Sponsored by the National Natural Science Foundation of China (60773129)the Excellent Youth Science and Technology Foundation of Anhui Province of China ( 08040106808)
文摘A novel classification algorithm based on abnormal magnetic signals is proposed for ground moving targets which are made of ferromagnetic material. According to the effect of diverse targets on earth's magnetism,the moving targets are detected by a magnetic sensor and classified with a simple computation method. The detection sensor is used for collecting a disturbance signal of earth magnetic field from an undetermined target. An optimum category match pattern of target signature is tested by training some statistical samples and designing a classification machine. Three ordinary targets are researched in the paper. The experimental results show that the algorithm has a low computation cost and a better sorting accuracy. This classification method can be applied to ground reconnaissance and target intrusion detection.
文摘When a gun fires the diffusion of chemical species from the propellant gas, such as CO, CO2, H2, H2O and N2, into the hot surface through the microcracks forms reaction products and speeds up the erosion process.Therefore, crack repairing and healing can be a possible measure for protecting against erosion of gun bore. The present study develops a novel nanocomposite with the size of 30 - 150 nm to repair and heal the microcracks so that the propellant gas can be prevented from reacting with the steel. Sample of gun steel 40CrNiMoV plate (10 mm× 10 mm × 2 mm) is prepared and a fishtail crack is generated through a repeated plastic deformation process. The crackrepairing results show that the fishtail crack become shorter and narrower. A new phase is formed, which is found to have the elements, such as Ca, La, from the raw materials of nanocomposite by energy spectrum analysis.
基金This work was financially supported by the National Natural Science Foundation of China (No.50235020).
文摘The composite films consisting of the titania gel impregnated with hydroxyapatite （HAP） submicron particles were prepared on commercial Ti6A14V plates processed by a sol-gel route. HAP powders were synthesized based on wet chemical precipitation method with Ca（NO3）2.4H2O and （NH4）2HPO4 as starting reagents. After being calcined at 900℃, HAP powders were ultrasonically scattered in ethanol to produce HAP sol. The titania sol was prepared using titanium （IV） isopropoxide {Ti[OCH（CH3）2]4} as precursor. Both the titania sol and the HAP/titania mixture were sequentially spin-coated on the substrates and calcined at various temperatures. The characteristics and mechanical adhesion of the composite films were investigated. The results show that the as-prepared films are dense, homogeneous, well-crystallized, and there is a good interfacial adhesion between the film and the substrate. The in vitro bioactivities of these films were discussed based on the analysis of the variations of Ca and P concentrations in the simulated body fluid and their surface morphologies against immersion time.
